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    Subject[RFC][PATCH -mm 2/3] PM: Disable usermode helper before hibernation/suspend
    Date
    From: Rafael J. Wysocki <rjw@sisk.pl>

    Use a hibernation and suspend notifier to disable the user mode helper before
    a hibernation/suspend and enable it after the operation.

    Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

    kernel/kmod.c | 31 +++++++++++++++++++++++++++++--
    1 file changed, 29 insertions(+), 2 deletions(-)

    Index: linux-2.6.22-rc3/kernel/kmod.c
    ===================================================================
    --- linux-2.6.22-rc3.orig/kernel/kmod.c 2007-05-27 18:56:44.000000000 +0200
    +++ linux-2.6.22-rc3/kernel/kmod.c 2007-05-27 19:43:35.000000000 +0200
    @@ -33,6 +33,8 @@
    #include <linux/kernel.h>
    #include <linux/init.h>
    #include <linux/resource.h>
    +#include <linux/notifier.h>
    +#include <linux/suspend.h>
    #include <asm/uaccess.h>

    extern int max_threads;
    @@ -46,6 +48,14 @@ static struct workqueue_struct *khelper_
    */
    char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";

    +/*
    + * If set, both call_usermodehelper_keys() and call_usermodehelper_pipe() exit
    + * immediately returning -EBUSY. Used for preventing user land processes from
    + * being created after the user land has been frozen during a system-wide
    + * hibernation or suspend operation.
    + */
    +static int usermodehelper_disabled;
    +
    /**
    * request_module - try to load a kernel module
    * @fmt: printf style format string for the name of the module
    @@ -251,6 +261,22 @@ static void __call_usermodehelper(struct
    complete(sub_info->complete);
    }

    +static int usermodehelper_pm_callback(struct notifier_block *nfb,
    + unsigned long action,
    + void *ignored)
    +{
    + switch (action) {
    + case PM_PRE_FREEZE:
    + usermodehelper_disabled = 1;
    + return NOTIFY_OK;
    + case PM_POST_THAW:
    + usermodehelper_disabled = 0;
    + return NOTIFY_OK;
    + }
    +
    + return NOTIFY_DONE;
    +}
    +
    /**
    * call_usermodehelper_keys - start a usermode application
    * @path: pathname for the application
    @@ -276,7 +302,7 @@ int call_usermodehelper_keys(char *path,
    struct subprocess_info *sub_info;
    int retval;

    - if (!khelper_wq)
    + if (!khelper_wq || usermodehelper_disabled)
    return -EBUSY;

    if (path[0] == '\0')
    @@ -319,7 +345,7 @@ int call_usermodehelper_pipe(char *path,
    };
    struct file *f;

    - if (!khelper_wq)
    + if (!khelper_wq || usermodehelper_disabled)
    return -EBUSY;

    if (path[0] == '\0')
    @@ -347,4 +373,5 @@ void __init usermodehelper_init(void)
    {
    khelper_wq = create_singlethread_workqueue("khelper");
    BUG_ON(!khelper_wq);
    + pm_notifier(usermodehelper_pm_callback, 0);
    }
    -
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